Drupal example - Get a default entity reference target from a field and check if a node has the default value

ExampleBlock.php

<?php


// Get the default target_id for this field from the field settings.
        $default_target_uuid = $loaded_node->field_some_entity_ref_field->getFieldDefinition()->get('default_value')[0]['target_uuid'];
        $default_media_entity = $this->entityRepository->loadEntityByUuid('media', $default_target_uuid);
        $default_media_entity_id = $default_media_entity->id();
        // Check if is the default one.
        $photo = $loaded_node->field_some_entity_ref_field->getValue();
        if ($photo[0]['target_id'] == $default_media_entity_id) {
          $total_staff_with_no_photo++;
        }